I play with some personal music on. It seems that when you enter in a multiplayer lobby, the game decrease the sound of everything, so that we can hear the voice chat (!?).

The problem is that also decrease the sound for whatever music player is working. Any way to stop that? It can get pretty distracting, especially since the sound will go up automatically at the end of the match.

Assuming you have windows 7(if not, then dig around the same area and you should find it), here's where you want to go.

Control panel/Sound/Communications tab/ Click on "Do Nothing"

That should do it...if it doesn't, then you'll have to look into some other tabs.

This also applies to people with vent issues and steam VC echoing, and vent not working properly....only in this instance you would go to the recording tab, and then click on microphone, then click properties, then the advanced tab, and uncheck all there.

The reason this applies to your music, is when you join a multiplayer lobby, the game accepts the voice chat of the other person (whether using it or not), and steam seems to take priority over other sounds for some reason. Changing these things tells windows don't change anything whether steam wants it or not...